4K HD Wallpaper: Mazda Furai
The super sport car in a great 4K image which can be downloaded free for personal use as desktop background and homescreen phone from courtesy of Dariusz Makowski.
Widescreen Desktop / Macbook (Retina): 2880x1800 (fits on: 2560x1600, 1920x1200, 1440x900)
High Definition HD 1080p: 1920x1080 (fits on: 1600x900, 1366x768, 1280x720)
Samsung Galaxy Tab & iPad: 2048x1536 (compatible with almost all tablets)
HTC, Samsung Galaxy & iPhone: 1080x1920 (compatible with many smartphones)